Scatter radiation reduction and correction are required for both medical and nonmedical X ray imaging applications. Due to scattered x-ray photons, the local contrast, Signal to Noise (SNR) and the data accuracy are deteriorated. Various methods to reduce and compensate for the scattering effect have been suggested and had being used. Considering Computerized Tomography (CT) imaging, for example, early CT scanners have used narrow fan beams and were assisted by antiscatter grids so scatter radiation was not a major issue in these systems. However, in modern CT scanners, large area X-ray detectors having a plurality of detector element arranged in rows and columns are used to perform multi-slice imaging. In these systems the width of a beam is significantly larger than in earlier single slice CT. Accordingly; the adverse effect of scattering is intensified.
In U.S. Pat. No. 5,666,391 to B. Ohnesorge, et al. (Sep. 9, 1997) the inventors suggest to correct for the scattered radiation by calculating a theoretical scattering distribution, based on the subject contour and shape as reconstructed from the data before the correction is applied, and subtracting the calculated scattering data from the actual collected data.
In U.S. Pat. No. 6,618,466 to N. Ruola (Sep. 9, 2003) the inventor suggests positioning an array of shields between the radiation source and the scanned subject, acquiring some views of the subject from some angels wherein the shielded areas of the detector are used to measure the scattered radiation, removing the shields array and scanning the subject without the array. The data collected in the first scan is used to calculate the scattering by interpolation for the entire array for all view angles and then to correct the data of the second scan.
In U.S. Pat. No. 7,336,759 to N. Masatak (Feb. 26, 2008) the inventor suggests collecting in addition to the wide beam scan data to be corrected, an additional set of projection data with narrow beam. The data with narrow beam is used to assess the effect of the scattered radiation at the same projections angles, and from these measurements to interpolate the scattering distribution of the wide beam.
However, none of these methods provides a solution for accurate measurement and compensation for the scattered radiation without adding steps to the imaging procedure and without exposing the subject to additional radiation.